Device for injecting a fuel into a combustion chamber of an internal combustion engine

ABSTRACT

The invention relates to a device for controlling the injection of a fuel into a combustion chamber ( 2 ) of a cylinder of a controlled-ignition or diesel internal combustion engine, the combustion chamber ( 2 ) being equipped with at least one spark plug ( 8 ). 
     According to the invention, the device comprises: 
     an adapter support ( 9 ) intended to be mounted on the cylinder head ( 3 ) of the engine, the adapter support being arranged to delimit, on the one hand, at least partially, an injection circuit ( 7 ) for the fuel and, on the other hand, a central passage ( 11 ) for mounting the spark plug ( 8 ), 
     and at least one control injector (I 1 ) for the fuel and one controlled injector (I 2 ) for a rinsing gas, the controlled injectors being mounted outside the combustion chamber, so that their outlets (s 1 , s 2 ) are connected to the inlet of the injection circuit ( 7 ).

FIELD OF THE INVENTION

The present invention relates to the technical field of internalcombustion engines and is aimed more particularly at systems for thedirect injection of a fuel into a combustion chamber of a cylinder of acontrol-ignition or diesel internal combustion engine.

In the conventional way, a system for the direct injection of fuelcomprises a controlled fuel injector capable of conveying the fueldirectly into the combustion chamber of a cylinder, via an injector ofgreater or lesser complexity able to withstand the flame front and abledirectly to withstand combustion. Now, it has become advantageous to usenatural gas in direct injection systems by way of a replacement fuel.

The benefit of the use of natural gas in controlled-ignition engines iswell known from the viewpoint of overall emissions of pollutants andcarbon monoxide. Even partial combustion of natural gas does not lead tothe production, in significant quantities, of toxic chemical compoundsor of sooty particles. Moreover, natural gas has a very high octanenumber making it possible for natural gas to be used in allnaturally-aspirated or supercharged controlled-ignition engines withoutany modification. The use of natural gas thus makes it possible tosignificantly increase the compression ratio or the boost ratio forprotection against pinging or against pre-ignition which is far greaterthan with gasoline or even with other liquefied gases.

It thus seems advantageous to replace the gasoline or liquefied gassupply to the engine with a system for the direct injection of naturalgas without reducing the reliability of the engine and at the same timeenjoying the ensuing increase in the compression ratio to improve theefficiency and power of the engine.

Many systems for the direct injection of a natural gas intended to bemounted on a combustion engine exist in the state of the art. However,the known technical solutions entail making significant modifications tothe cylinder head of the engine delimiting the combustion chamber. Inaddition, such injection systems generally have a relatively complexdesign exhibiting a high cost.

SUMMARY OF THE INVENTION

One object of the invention is therefore to propose a device for thedirect injection of a fuel other than the one initially intended whileat the same time being designed to be mounted in place of a spark plugor of the injector in a diesel engine, so as not to entail substantialmodifications to the engine.

In order to achieve such an objective, the device according to theinvention comprises:

an adapter support intended to be mounted on the cylinder head of theengine, the adapter support being arranged to delimit, on the one hand,at least partially, an injection circuit for the fuel and, on the otherhand, a central passage for mounting the spark plug,

and at least one controlled injector for the fuel and one controlledinjector for a rinsing gas, the controlled injectors being mountedoutside the combustion chamber, so that their outlets are connected tothe inlet of the injection circuit.

The device according to the invention also makes it possible to inject afuel directly into a combustion chamber of a cylinder of acontrolled-ignition or diesel internal combustion engine usingconventional injectors customarily used for indirect injection.

One object of the invention is also to propose a technique allowingcomplete injection of the fuel into the combustion chamber of a cylinderof a combustion engine.

To achieve such an objective, the device according to the inventioncomprises control means making it possible, for each compression stroke,and after the air intake port has closed, to drive:

the fuel injector so as to inject fuel into the combustion chamber andthrough the injection circuit so as to leave a determined length of timebetween the end of injection of the fuel and the point of ignition,

the injector of the rinsing gas so as to inject a rinsing gas throughthe injection circuit at least during the period of time so as to drivethe fuel along and convey it into the combustion chamber with a view toit burning in said chamber.

The direct injection device according to the invention is designed to,on the one hand, ensure complete combustion of the fuel inside thecombustion chamber and, on the other hand, inject a fuel other than theone initially intended while at the same time not entailing majormodifications to such an engine.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other features will become apparent from the description givenhereinbelow with reference to the appended drawings which, by way ofnonlimiting example, show some embodiments and implementations of thesubject of the invention.

FIG. 1 is a schematic view in section/elevation of a first embodiment ofan injection device according to the invention.

FIGS. 2 and 3 are views illustrating other alternative forms ofembodiment of a control device according to the invention.

FIG. 4 is a view from underneath taken more or less along the linesIV—IV of FIG. 3.

FIGS. 5 and 6 are schematic views showing other exemplary embodiments ofthe injection device according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an exemplary embodiment of a device 1 for the directinjection of a fuel into a combustion chamber 2 assigned to a cylinder,not depicted, of a controlled-ignition or diesel internal combustionengine. The combustion chamber 2, which is depicted only in part becauseit does not form part of the subject of the invention, is equipped inthe conventional way with at least one air intake port. In the case of afour-stroke engine, this air intake port constitutes an intake valveassociated with an exhaust valve, not depicted. The combustion chamber 2is closed in the conventional way by a cylinder head 3. In theconventional way, the cylinder head 3 has, for each cylinder, an accesswell 4 communicating with the combustion chamber 2.

According to the invention, the device 1 comprises at least onecontrolled injector 1, for a fuel and one controlled injector I₂ for arinsing gas. In the preferred exemplary embodiment described below, thefuel used is natural gas while the rinsing gas is air or possiblyexhaust gases. As a preference, the injectors I₁, I₂ are electromagneticinjectors conventionally marketed and used in indirect injection. Thecontrolled injectors I₁, and I₂ are mounted outside the combustionchamber 2 on an injector holder 5. The device 1 comprising aninjector—spark plug holder unit 6 provided with an injection circuit 7designed to convey at least the fuel into the combustion chamber 2. Theinjector circuit 7 communicates, on one side, with the outlets s₁, s₂ ofthe injectors I₁, I₂ and, on the other side, with the combustion chamber2. The injector—spark plug holder unit 6 also comprises a spark plug 8.

According to one advantageous embodiment feature, the injector-sparkplug holder unit 6 is designed to be mounted on the cylinder head 3 ofthe engine without making substantial modifications to the latter. Thus,the injector-spark plug holder unit 6 has an adapter support 9 intendedto be mounted on the cylinder head 3 inside the well 4. According to anadvantageous exemplary embodiment, the adapter support 9 has a tubularoverall shape and externally and, for example at its lower end, has athreaded mounting part 9 a intended to cooperate with a complementarytapped thread 10 made in the well 4 of the cylinder head. According to apreferred embodiment, the threaded part 9 a cooperates with the tappedthread 10 corresponding to the tapping for screwing in a conventionalspark plug. It is to be understood that the adapter support 9 is mountedin place of a conventional spark plug. In the case of the injectionsystem 1 according to the invention being mounted on an engine of thediesel type, the adapter support 9 is mounted in place of the injector.In the latter exemplary embodiment, it must not be precluded for thewell 4 that takes such an injector to be arranged to take the adaptersupport 9 according to the invention.

The adapter support 9 has a central passage 11 passing right throughsaid support and allowing the spark plug 8 to be mounted. According to apreferred feature of the embodiment illustrated more particularly inFIGS. 1 to 3, the central passage 11 comprises, for example at its upperend, a tapped thread 13 intended to cooperate with a screwthread made onthe spark plug 8. The spark plug 8 has, by comparison with aconventional spark plug, smaller diametral dimensions so as to allow itto be mounted inside the adapter support 9 which, in a preferredexemplary embodiment, takes the place of a conventional spark plug. Thespark plug 8 thus has an electrically insulating barrel 14 from the endof which the central electrode 15 which extends into the combustionchamber 2 protrudes. According to a preferred but nonlimitingembodiment, the adapter support 9 is designed to delimit a groundelectrode 17 extending conventionally close to the central electrode 15.Such a spark plug 8 comprises, in the conventional way, at the oppositeend of the insulating barrel 14, an electrical-connecting nipple 18 anda tightening nut 19 allowing the spark plug 8 to be mounted on theadapter support 9.

The adapter support 9 externally comprises a shoulder 21 surmounting thethreaded part 9 a, so as to bear, via a sealing gasket 22, against thebottom 23 of a counterbore made in the mounting well 4. Screwing theadapter support 9 onto the cylinder head 3 thus makes it possible tomount the spark plug 8 and to seal the combustion chamber 2.

The adapter support 9 is arranged to delimit, at least partially, theinjection circuit 7 for the fuel. In the exemplary embodimentillustrated in FIG. 1, the injection circuit 7 comprises an internalcircuit 27 arranged in the adapter support 9 and communicating, on oneside, with the combustion chamber 2 and, on the other side, with a line28 extending externally from the adapter support 9. This line 28, whichis mounted in any appropriate way on the injector holder 5 and theadapter support 9, communicates with the outlets s₁, s₂ of the injectorsI₁, I₂. This line 28, consisting of a high-pressure tube, forms, withthe internal circuit 27, the injection circuit 7 for the fuel. It is tobe noted that in an exemplary embodiment illustrated more particularlyin FIG. 2, the line 28 is mounted on a sealing plug 29 inserted betweenthe adapter support 9 and the tightening nut 19 of the spark plug 8.Thus, mounting the spark plug 8 on the adapter support 9 makes itpossible to provide sealing between the line 28 and the internal circuit27 formed in the adapter support 9.

In the exemplary embodiment illustrated in FIG. 1, the internal circuit27 formed in the adapter support 9 consists of an annular chamberdelimited by the central passage 11 and the insulting barrel 14 of thespark plug 8. This annular chamber 27 which opens into the combustionchamber 2 around the spark plug 8 communicates with an annularcounterbore 31 produced inside the adapter support 9 to constitute adistribution chamber connected to the line 28.

In the example illustrated more particularly in FIGS. 3 and 4, theinternal circuit 27 of the injection circuit 7 consists of a series ofducts 32 formed in the adapter support 9 on the same radius and parallelto one another. These ducts 32 communicate, on one side, with thecombustion chamber 2 and, on the other side, with the annularcounterbore 31 connected to the line 28. The ducts 32 thus open onto thetransverse face of the adapter support 9 extending inside the combustionchamber and are distributed around the central electrode of the sparkplug 8 allowing good dispersion of the fuel with the air contained inthe combustion chamber 2.

FIG. 5 schematically illustrates another exemplary embodiment of theinternal circuit 27 of the injection circuit. In this example, theinternal circuit 27 consists of a tubular pipe 34 opening, on one side,into the combustion chamber 2 and communicating, on the other side, withthe line 28 connected to the outlets of the injectors I₁, I₂. Thistubular pipe 34 is connected to an electrical supply by any appropriatemeans so as to constitute the central electrode 15 of the spark plug 8.For example, this tubular electrode or pipe 34 is surrounded by theelectrically insulating barrel 14, of which the part extending away fromthe combustion chamber 2, serves to mount a connecting endpiece 35 of anelectric supply cable 36 which provides the electrical connection withthe tubular pipe 34. Of course, the line 28 is made of an electricallyinsulating material. The electrically insulating barrel 14 is mountedinside the adapter support 9 which delimits the ground electrode 17.

According to another feature of the invention, the device 1 according tothe invention also comprises control means, which have not been depictedbut which are known per se, making it possible to drive the operation ofthe injectors I₁, and I₂ with a view to implementing a method forcontrolling the injection of fuel according to the invention.

These control means make it possible, for each compression stroke, andafter an air intake port of the cylinder has closed, to drive:

the fuel injector I₁, so as to inject fuel into the combustion chamber 2and through the injection circuit 7 so as to leave a determined lengthof time between the end of injection of the fuel and the point ofignition,

the injector I₂ of the rinsing gas so as to inject a rinsing gas throughthe injection circuit 7 at least during the period of time so as todrive the fuel along and convey it into the combustion chamber 2 with aview to it burning in said chamber.

Thus, for each compression stroke, once the intake port of theassociated cylinder has closed, the fuel injector I₁ is controlled so asto inject the fuel, for a determined injection time which conventionallyis dependent upon the desired load and the customary various combustionmanagement parameters. Such injection of fuel is ended a few tens ofdegrees before the point of ignition so as to leave a determined periodof time between the end of the injection of fuel and the point ofignition, during which period of time the injector I₂ of rinsing gasdelivers a sufficient amount of rinsing gas to drive the fuel along andconvey it into the combustion chamber 2 with a view to it being burntupon ignition. This then gives a kind of rinsing of the injectioncircuit 7 making it possible to eliminate any trace of fuel and, inparticular, of methane contained in the circuit and which would be lateto arrive in the chamber for burning if the production of a jet ofrinsing gas had not occurred.

According to the foregoing description, the subject of the inventionmakes it possible to ensure complete combustion of the fuel delivered bythe injector by sending, prior to ignition, a jet of rinsing gas intothe injection circuit. Furthermore, the injection device 1 according tothe invention is designed to be mounted, without modifications to thecylinder head, in place of the spark plug on a gasoline engine or on adiesel engine in place of the injector, while at the same time ensuringcomplete combustion of the fuel injected, likely to be found in theinjection circuit. In addition, such an injection device 1 implementsconventional injectors and a spark plug which is special-purpose but ofa design similar to the known one. In this respect, it may beadvantageous to use a 10 mm spark plug used in competitive motoring ascompared with special-purpose production of the spark plug. Thus, as ismore particularly apparent from FIG. 6, fitting the injection device 1according to the invention is relatively simple in that all that isrequired is the production of an adapter support 9 designed to cooperatewith the tapped thread 10 conventionally made in the cylinder head 3.Such an adapter support 9 supports the spark plug 8 and has an internalcircuit 27 connected to the line 28.

The injection device 1 makes it possible relatively easily to change thetype of fuel used by an engine, for example, to natural gas. However, toincrease the multi-functionality of such a system, provision may be madefor an additional injector designed, for example, to deliver gasoline orliquefied petroleum gas, to be mounted on the injector holder 5. In thisalternative form, the injection of the rinsing gas, such as air, is alsoperformed during the injection of the fuel so as to perform pre-mixingprior to introduction into the combustion chamber 2. Of course, theinjection of the rinsing gas is continued after the end of injection ofthe fuel so as to drive said fuel from the injection circuit, asexplained above. According to this exemplary embodiment, the internalinjection circuit 27 is as per the one described in FIGS. 3 and 4employing concentric ducts 32, so that the carburetted mixture does notfind itself in contact with the insulating barrel 14 of the spark plug.

The invention is not restricted to the examples described and depicted,because various modifications can be made thereto without departing fromits scope.

What is claimed is:
 1. A device for controlling the injection of a fuelinto a combustion chamber (2) of a cylinder of a controlled-ignition ordiesel internal combustion engine, the combustion chamber (2) beingequipped with at least one spark plug (8), characterized in that itcomprises: an adapter support (9) intended to be mounted on the cylinderhead (3) of the engine, the adapter support being arranged to delimit,on the one hand, at least partially, an injection circuit (7) for thefuel and, on the other hand, a central passage (11) for mounting thespark plug (8), and at least one controlled injector (I₁) for the fueland one controlled injector (I₂) for a rinsing gas, the controlledinjectors being mounted outside the combustion chamber, so that theiroutlets (s₁, s₂) are connected to the inlet of the injection circuit(7).
 2. The device as claimed in claim 1, characterized in that theadapter support (9) comprises a threaded mounting part (9 a) intended tocooperate with a tapped thread (10) formed in the cylinder head (3) andcorresponding to the tapped thread for screwing in a conventional sparkplug or to a tapped thread formed in the passage for mounting a dieselinjector.
 3. The device as claimed in claim 2, characterized in that theadapter support (9) comprises a threaded part (9 a) surmounted by ashoulder (21) intended to bear, via a sealing gasket (22), against thebottom (23) of a mounting well formed in the cylinder head.
 4. Thedevice as claimed in claim 1, characterized in that the adapter support(9) comprises a central passage (11) which is partially tapped (13) toallow the spark plug (8) to be mounted by screwing.
 5. The device asclaimed in claim 1, characterized in that the adapter support (9)comprises, in its part opening into the combustion chamber, the groundelectrode (17) of the spark plug (8).
 6. The device as claimed in claim1, characterized in that the injection circuit (7) comprises an internalcircuit (27) formed in the adapter support (9) and communicating, on oneside, with the combustion chamber (2) and, on the other side, with aline (28) connected to the injector outlets (s₁, s₂).
 7. The device asclaimed in claim 6, characterized in that the internal circuit (27) ofthe injection circuit (7) consists of an annular chamber delimitedbetween the central passage (11) and the spark plug (8) andcommunicating with the line (28).
 8. The device as claimed in claim 6,characterized in that the internal circuit (27) of the injection circuit(7) consists of a series of ducts (32) formed in the adapter support (9)and communicating, on one side, with the combustion chamber (2) and, onthe other side, with a distribution chamber (31) communicating with theline (28).
 9. The device as claimed in claim 6, characterized in thatthe internal circuit (27) of the injection circuit (7) consists of atubular pipe opening into the combustion chamber (2) and communicatingwith the line (28) connected to the injector outlets, said tubular pipebeing electrically connected in order to constitute the centralelectrode of the spark plug (8).
 10. The device as claimed in claim 6,characterized in that the line has one end mounted on an injector holderand communicating with the injector outlets (s₁, s₂) and an opposite endmounted on a sealing plug inserted between the adapter support and thespark plug.
 11. The device as claimed in claim 10, characterized in thatthe injector holder (5) is equipped with a controlled injector (I₁) forthe fuel of the natural gas type and/or with a controlled injector forgasoline or liquefied petroleum gas.
 12. The device as claimed in claim1, characterized in that it comprises control means making it possible,for each compression stroke, and after an air intake port has closed, todrive: the fuel injector so as to inject fuel into the combustionchamber and through the injection circuit so as to leave a determinedlength of time between the end of injection of the fuel and the point ofignition, the injector of the rinsing gas so as to inject a rinsing gasthrough the injection circuit at least during the period of time so asto drive the fuel along and convey it into the combustion chamber with aview to it burning in said chamber.
 13. The device as claimed in claim12, characterized in that the control means make it possible to controlthe injection of the rinsing gas during injection of the fuel so as toperform pre-mixing prior to introduction into the combustion chamber(2).
 14. The device as claimed in claim 12, characterized in that thefuel injector (I₁) injects natural gas by way of fuel.
 15. The device asclaimed in claim 12, characterized in that the fuel injector (I₁)injects gasoline or liquefied petroleum gas by way of fuel.
 16. Thedevice as claimed in claim 12, characterized in that the injector of arinsing gas injects air or exhaust gases by way of rinsing gas.
 17. Acylinder head for a combustion engine, characterized in that it isequipped with a control device as claimed in one of claims 1 to
 16. 18.The device as claimed in claim 7, characterized in that the line has oneend mounted on an injector holder and communicating with the injectoroutlets (s₁, s₂) and an opposite end mounted on a sealing plug insertedbetween the adapter support and the spark plug.
 19. The device asclaimed in claim 8, characterized in that the line has one end mountedon an injector holder and communicating with the injector outlets (s₁,s₂) and an opposite end mounted on a sealing plug inserted between theadapter support and the spark plug.
 20. The device as claimed in claim9, characterized in that the line has one end mounted on an injectorholder and communicating with the injector outlets (s₁, s₂) and anopposite end mounted on a sealing plug inserted between the adaptersupport and the spark plug.
 21. The device as claimed in claim 1,characterized in that it comprises control means making it possible, foreach compression stroke, and after an air intake port has closed, todrive: the fuel injector so as to inject fuel into the combustionchamber and through the injection circuit so as to leave a determinedlength of time between the end of injection of the fuel and the point ofignition, the injector of the rinsing gas so as to inject a rinsing gasthrough the injection circuit at least during the period of time so asto drive the fuel along and convey it into the combustion chamber with aview to it burning in said chamber.